Mon·Feb 5, 2018Monday·February 5, 2018

1. 01*

   Exploring hyperon structure with electromagnetic transverse densities

   Jose Manuel Alarcón · Astrid N. Hiller Blin · Manuel J. Vicente Vacas · Christian Weiss

   We explore the structure of the spin-1/2 flavor-octet baryons (hyperons) through their electromagnetic transverse densities. The transverse densities describe the distribution of charge and magnetization at fixed light-front time and enable a spatial representation of the baryons as relativistic systems. At peripheral distances b~1/M_pi the transverse densities are computed using a new method that combines chiral effective field theory and dispersion analysis. The peripheral isovector densities arise from two-pion exchange, which includes the rho-meson resonance through elastic unitarity. The isoscalar densities are estimated from vector meson exchange (omega, phi). We find that the "pion cloud" in the charged Sigma hyperons is comparable to the nucleon, while in the Xi it is suppressed. The Lambda-Sigma^0 transition density is pure isovector and represents a clear manifestiation of peripheral two-pion dynamics.

   hep-phnucl-thFew Body Syst.(2018)·0 citations
2. 02*

   Dense Instanton-Dyon Liquid Model: Diagrammatics

   Yizhuang Liu🇺🇸 · Edward Shuryak🇺🇸 · Ismail Zahed🇺🇸

   We revisit the instanton-dyon liquid model in the confined phase by using a non-linear Debye-Huckel (DH) resummation for the Coulomb interactions induced by the moduli, followed by a cluster expansion. The organization is shown to rapidly converge and yields center symmetry at high density. The dependence of these results on a finite vacuum angle are also discussed. We also formulate the hypernetted chain (HCN) resummation for the dense instanton-dyon liquid and use it to estimate the liquid pair correlation functions in the DH limit. At very low temperature, the dense limit interpolates between chains and rings of instanton-anti-instanton-dyons and a bcc crystal, with strong topological and magnetic correlations.

   hep-phhep-lathep-thPRD(2018)·7 citations
3. 03*

   Neutrino-mass differences studied in a model with one basic neutrino

   Wen-ge Wang🇨🇳

   In this paper, we propose and study a model, in which there exists only one basic neutrino. Basically, the Lagrangian of the model is obtained from the Lagrangian in the Glashow-Weinberg-Salam electroweak theory by reducing the three flavor neutrinos there to one basic neutrino. In this model, neutrino states with a fixed flavor are interpreted as certain superpositions of states of the basic neutrino and states of the related charged lepton. Neutrino mass states are associated with low-lying eigenstates of the total Hamiltonian. We derive an approximate expression for a ratio of neutrino-mass differences, which gives a value $17$ for the ratio, about half of the experimental result of $33$.

   hep-ph0 citations
4. 04*

   QCD axion dark matter from long-lived domain walls during matter domination

   Keisuke Harigaya🇺🇸 · Masahiro Kawasaki🇯🇵

   The domain wall problem of the Peccei-Quinn mechanism can be solved if the Peccei-Quinn symmetry is explicitly broken by a small amount. Domain walls decay into axions, which may account for dark matter of the universe. This scheme is however strongly constrained by overproduction of axions unless the phase of the explicit breaking term is tuned. We investigate the case where the universe is matter-dominated around the temperature of the MeV scale and domain walls decay during this matter dominated epoch. We show how the viable parameter space is expanded.

   hep-phastro-ph.COPLB(2018)·34 citations
5. 05*

   Post-Newtonian particle physics in curved spacetime

   Matt Visser (Victoria University of Wellington)🇳🇿

   In three very recent papers, (an initial paper by Morishima and Futamase, and two subsequent papers by Morishima, Futamase, and Shimizu), it has been argued that the observed experimental anomaly in the anomalous magnetic moment of the muon might be explained using general relativity. It is my melancholy duty to report that these articles are fundamentally flawed in that they fail to correctly implement the Einstein equivalence principle of general relativity. Insofar as one accepts the underlying logic behind these calculations (and so rejects general relativity) the claimed effect due to the Earth's gravity will be swamped by the effect due to Sun (by a factor of fifteen), and by the effect due to the Galaxy (by a factor of two thousand). In contrast, insofar as one accepts general relativity, then the claimed effect will be suppressed by an extra factor of [(size of laboratory)/(radius of Earth)]^2. Either way, the claimed effect is not compatible with explaining the observed experimental anomaly in the anomalous magnetic moment of the muon.

   hep-phgr-qc18 citations
6. 06*

   EPPS16 - Bringing nuclear PDFs to the LHC era

   Kari J. Eskola🇫🇮 · Petja Paakkinen🇫🇮 · Hannu Paukkunen🇫🇮 · Carlos A. Salgado🇪🇸

   We report on EPPS16, the first global analysis of nuclear parton distribution functions (nPDFs) to include LHC data. Also for the first time, a full flavour dependence of nPDFs is allowed. While the included Z and W data are found to have insufficient statistics to yield stringent constraints, the CMS 5.02 TeV proton-lead dijet data prove crucial in setting the shape of nuclear gluon modifications. With these and other observables being measured in proton-lead runs, we are experiencing a shift of nPDFs to the LHC precision era.

   hep-phPoS(2019)·4 citations
7. 07*

   Photon or meson formation in $J/\psi$ decays into $p\overline{p}$

   J.-P. Dedonder🇫🇷 · B. Loiseau🇫🇷 · S. Wycech🇵🇱

   The measurements of the $J/\psi \to \gamma p\overline{p}$ decays by the BES Collaboration indicate an enhancement at the $p\overline{p}$ threshold which, however, is not present in the J/$\psi$ decays into $\omega p\overline{p}$ and into $\pi p\overline{p}$. Here, two processes for describing the decays $J/\psi \to \mathcal{B}p\overline{p}$ where $\mathcal{B}=\gamma ,\omega$ are presented in some detail and the cases $\mathcal{B}=\varphi ,\pi$ are briefly touched on. The first one, applied not only to the radiative decay to reproduce the threshold peak but also to the $\omega p\overline{p}$ decay channel to improve the description of the spectrum, postulates a direct emission of the boson before the baryon pair is formed. The second process assumes that the boson $\mathcal{B}$ is emitted from the baryon pair following the $J/\psi$ decay and includes for the decays into $\gamma p\overline{p}$ a final state nucleon-antinucleon interaction based on the Paris $N\overline{N}$ potential. The reproduction of the $p\overline{p}$ distribution in the $J/\psi \to \omega p\overline{p}$ decays needs a final state interaction involving a $N(2050)3/2^{-}$ resonance. The photon- and meson-emission rates are reproduced in a semi-quantitative way.

   hep-phhep-exnucl-thPRC(2018)·9 citations
8. 08*

   Footprints of leptoquarks: from $R_{K^{(\ast )}}$ to $K\to \pi \nu \bar{\nu }$

   S. Fajfer🇸🇮 · N. Košnik🇸🇮 · L. Vale Silva🇬🇧

   Rare $K\to \pi \nu \bar{\nu }$ decays, being dominated by short distance contributions within the Standard Model (SM), open a window for New Physics (NP) searches at low energies. The $K\to \pi \nu \bar{\nu }$ branching ratios are expected to be measured with $\sim 10\%$ accuracies by NA62/CERN and KOTO/JPARC. The theoretical uncertainties of branching ratios within the SM are well under control. In the $B$ sector, it is tentative to explain the $B$-meson anomalies $R_{D^{(\ast )}}$ and/or $R_{K^{(\ast )}}$ by effects of physics beyond the SM. Although NP seems to be present in the third fermion generation it might also manifest in the flavor changing neutral current transition $s\to d$. Together with the anticipated good experimental sensitivities and accurate theoretical predictions for $K\to \pi \nu \bar{\nu }$, this motivates studies of correlated effects of NP in rare $K\to \pi \nu \bar{\nu }$ and $B\to K^{(\ast )}{\mu }^{+}{\mu }^{-}$ decays. Here we consider the loop induced effects in $K\to \pi \nu \bar{\nu }$ in two leptoquark models designed to address lepton-flavor universality violation in the $R_{K^{(\ast )}}$ anomalies.

   hep-phEPJC(2018)·71 citations
9. 09*

   Dispersive approach to non-Abelian axial anomaly

   Sergey Khlebtsov🇷🇺 · Yaroslav Klopot🇷🇺 · Armen Oganesian🇷🇺 · Oleg Teryaev🇷🇺

   Manifestations of strong and electromagnetic axial anomalies in two-photon decays of $\eta$ and ${\eta }^{\prime }$ mesons are studied. Applying dispersive approach to axial anomaly in the singlet current, we obtain an anomaly sum rule containing strong and electromagnetic anomaly contributions. The relevant low energy theorem was generalized to the case of mixed states and used to evaluate the subtraction constant of the strong anomaly-related form factor $⟨0|G\tilde{G}|\gamma \gamma ⟩$. We made a numerical estimation of the contributions of gluon and electromagnetic anomalies to the two-photon decays of $\eta$ and ${\eta }^{\prime }$ mesons and found significant suppression of the gluon anomaly contribution.

   hep-phPRD(2019)·7 citations
10. 10*

    Top-philic dark matter within and beyond the WIMP paradigm

    Mathias Garny🇩🇪 · Jan Heisig🇩🇪 · Marco Hufnagel🇩🇪 · Benedikt Lülf🇩🇪

    We present a comprehensive analysis of top-philic Majorana dark matter that interacts via a colored t-channel mediator. Despite the simplicity of the model -- introducing three parameters only -- it provides an extremely rich phenomenology allowing us to accommodate the relic density for a large range of coupling strengths spanning over six orders of magnitude. This model features all `exceptional' mechanisms for dark matter freeze-out, including the recently discovered conversion-driven freeze-out mode, with interesting signatures of long-lived colored particles at colliders. We constrain the cosmologically allowed parameter space with current experimental limits from direct, indirect and collider searches, with special emphasis on light dark matter below the top mass. In particular, we explore the interplay between limits from Xenon1T, Fermi-LAT and AMS-02 as well as limits from stop, monojet and Higgs invisible decay searches at the LHC. We find that several blind spots for light dark matter evade current constraints. The region in parameter space where the relic density is set by the mechanism of conversion-driven freeze-out can be conclusively tested by R-hadron searches at the LHC with 300\,fb${}^{-1}$.

    hep-phastro-ph.COPRD(2018)·70 citations
11. 11*

    Nonmetricity formulation of general relativity and its scalar-tensor extension

    Laur Järv🇪🇪 · Mihkel Rünkla🇪🇪 · Margus Saal🇪🇪 · Ott Vilson🇪🇪

    Einstein's celebrated theory of gravitation can be presented in three forms: general relativity, teleparallel gravity, and the rarely considered before symmetric teleparallel gravity. Extending the latter, we introduce a new class of theories where a scalar field is coupled nonminimally to nonmetricity $Q$, which here encodes the gravitational effects like curvature $R$ in general relativity or torsion $T$ in teleparallel gravity. We point out the similarities and differences with analogous scalar-curvature and scalar-torsion theories by discussing the field equations, role of connection, conformal transformations, relation to $f(Q)$ theory, and cosmology. The equations for spatially flat universe coincide with those of teleparallel dark energy, thus allowing to explain accelerating expansion.

    ↳ gr-qchep-phhep-thPRD(2018)·245 citations
12. 12*

    K${}^{-}$ over K${}^{+}$ multiplicity ratio for kaons produced in DIS with a large fraction of the virtual-photon energy

    R. Akhunzyanov · M.G. Alexeev · G.D. Alexeev · A. Amoroso · V. Andrieux · N.V. Anfimov · V. Anosov · A. Antoshkin · K. Augsten · W. Augustyniak · C.D.R. Azevedo · B. Badelek and 199 other authors

    The K${}^{-}$ over K${}^{+}$ multiplicity ratio is measured in deep-inelastic scattering, for the first time for kaons carrying a large fraction $z$ of the virtual-photon energy. The data were obtained by the COMPASS collaboration using a 160 GeV muon beam and an isoscalar ${}^6$LiD target. The regime of deep-inelastic scattering is ensured by requiring $Q^2>1$ (GeV/$c{)}^2$ for the photon virtuality and $W>5$ GeV/$c^2$ for the invariant mass of the produced hadronic system. Kaons are identified in the momentum range from 12 GeV/$c$ to 40 GeV/$c$, thereby restricting the range in Bjorken-$x$ to $0.01<x<0.40$. The $z$-dependence of the multiplicity ratio is studied for $z>0.75$. For very large values of $z$, $i.e.$ $z>0.8$, we observe the kaon multiplicity ratio to fall below the lower limits expected from calculations based on leading and next-to-leading order perturbative quantum chromodynamics. Also, the kaon multiplicity ratio shows a strong dependence on the missing mass of the single-kaon production process. This suggests that within the perturbative quantum chromodynamics formalism an additional correction may be required, which takes into account the phase space available for hadronisation.

    ↳ hep-exhep-phPLB(2018)·22 citations
13. 13*

    Induced Affine Inflation

    Hemza Azri🇹🇷 · Durmus Demir🇹🇷

    Induced gravity, metrical gravity in which gravitational constant arises from vacuum expectation value of a heavy scalar, is known to suffer from Jordan frame vs. Einstein frame ambiguity, especially in inflationary dynamics. Induced gravity in affine geometry, as we show here, leads to an emergent metric and gravity scale, with no Einstein-Jordan ambiguity. While gravity is induced by the vacuum expectation value of the scalar field, nonzero vacuum energy facilitates generation of the metric. Our analysis shows that induced gravity results in a relatively large tensor-to-scalar ratio in both metrical and affine gravity setups. However, the fact remains that the induced affine gravity provides an ambiguity-free framework.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRD(2018)·31 citations
14. 14*

    Impact of cosmic-ray physics on dark matter indirect searches

    Daniele Gaggero🇳🇱 · Mauro Valli🇮🇹

    The quest for the elusive dark matter (DM) that permeates the Universe (and in general the search for signatures of Physics beyond the Standard Model at astronomical scales) provides a unique opportunity and a tough challenge to the high-energy astrophysics community. In particular, the so-called DM indirect searches - mostly focused on a class of theoretically well-motivated DM candidates such as the weakly-interacting massive particles - are affected by a complex astrophysical background of cosmic radiation. The understanding and modeling of such background requires a deep comprehension of an intricate classical plasma physics problem, i.e. the interaction between high-energy charged particles, accelerated in peculiar astrophysical environments, and magneto-hydrodynamic turbulence in the interstellar medium of our Galaxy. In this review we highlight several aspects of this exciting interplay between the most recent claims of DM annihilation/decay signatures from the sky and the Galactic cosmic-ray research field. Our purpose is to further stimulate the debate about viable astrophysical explanations, discussing possible directions that would help breaking degeneracy patterns in the interpretation of current data. We eventually aim to emphasize how a deep knowledge on the physics of CR transport is therefore required to tackle the DM indirect search program at present and in the forthcoming years.

    ↳ astro-ph.HEastro-ph.COhep-phAdv.High Energy Phys.(2018)·21 citations
15. 15*

    Application of Nilsson model for deformed nucleus in relativistic heavy ion collisions

    S. K. Tripathy🇮🇳 · M. Younus🇮🇳 · P. K. Sahu🇮🇳 · Z. Naik🇮🇳

    Electron scattering methods, involving nucleus which have little or no intrinsic deformation suggest nucleon distribution to be of Fermi type. This distribution is further parameterised as Wood Saxon (WS) distribution, where an uniform charge density with smoothed-out surface have been implemented. Incorporating shape modification in WS, earlier attempts were made to explain observables in deformed nuclear collisions, such as charged particle multiplicity. In this work, we use an alternate approach known as Nilsson model or Modified Harmonic Oscillator (MHO), to explain charged particle multiplicity in U+U collisions at top RHIC energy. We have implemented the formalism in HIJING model and we found that the model describes the experimental data to an extent.

    ↳ nucl-thhep-ph0 citations
16. 16*

    Bayesian study of relativistic open and hidden charm in anisotropic lattice QCD

    Aoife Kelly🇮🇪 · Alexander Rothkopf🇩🇪 · Jon-Ivar Skullerud🇮🇪

    We present the first combined study of correlators and spectral properties of charmonium and open-charm-mesons at finite temperature using a fully relativistic lattice QCD approach. The QCD medium is captured by second generation anisotropic 24^3xN_t lattices from the FASTSUM collaboration, including 2+1 flavors of clover discretized quarks with m_pi~380 MeV. Two Bayesian methods are deployed to reconstruct the spectral functions, the recent BR method as well as the Maximum Entropy Method with Fourier basis. We take particular care to disentangle genuine in-medium effects from method artifacts with the help of the reconstructed correlator. Consistent with the direct inspection of correlators, we observe no significant in-medium modification for J/Psi and eta_c around the crossover, while the chi_c states on the other hand show clear changes around the transition. At the highest temperature, T=352 MeV, J/Psi and eta_c also exhibit discernible changes compared to the vacuum. For D mesons around $T_c$, no significant modifications are observed, but we find clear indications that no bound state survives at the highest temperature of T=352 MeV. Above T_c we discover a significant difference between D and D* mesons, the latter being much more strongly affected by the medium.

    ↳ hep-lathep-phnucl-thPRD(2018)·41 citations
17. 17*

    On the zero-crossing of the three-gluon Green's function from lattice simulations

    A. Athenodorou🇨🇾 · Ph. Boucaud🇫🇷 · F. De Soto🇪🇸 · J. Rodríguez-Quintero🇪🇸 · S. Zafeiropoulos🇩🇪

    We report on some efforts recently made in order to gain a better understanding of some IR properties of the 3-point gluon Green's function by exploiting results from large-volume quenched lattice simulations. These lattice results have been obtained by using both tree-level Symanzik and the standard Wilson action, in the aim of assessing the possible impact of effects presumably resulting from a particular choice for the discretization of the action. The main resulting feature is the existence of a negative logaritmic divergence at zero-momentum, which pulls the 3-gluon form factors down at low momenta and, consequently, yields a zero-crossing at a given deep IR momentum. The results can be correctly explained by analyzing the relevant Dyson-Schwinger equations and appropriate truncation schemes.

    ↳ hep-lathep-phEPJ Web Conf.(2018)·3 citations
18. 18*

    Survival amplitude, instantaneous energy and decay rate of an unstable system: Analytical results

    K. Raczynska🇵🇱 · K. Urbanowski🇵🇱

    We consider a model of a unstable state defined by the truncated Breit-Wigner energy density distribution function. An analytical form of the survival amplitude $a(t)$ of the state considered is found. Our attention is focused on the late time properties of $a(t)$ and on effects generated by the non--exponential behavior of this amplitude in the late time region: In 1957 Khalfin proved that this amplitude tends to zero as $t$ goes to the infinity more slowly than any exponential function of $t$. This effect can be described using a time-dependent decay rate $\gamma (t)$ and then the Khalfin result means that this $\gamma (t)$ is not a constant but at late times it tends to zero as $t$ goes to the infinity. It appears that the energy $E(t)$ of the unstable state behaves similarly: It tends to the minimal energy $E_{min}$ of the system as $t\to \infty$. Within the model considered we find two first leading time dependent elements of late time asymptotic expansions of $E(t)$ and $\gamma (t)$. We discuss also possible implications of such a late time asymptotic properties of $E(t)$ and $\gamma (t)$ and cases where these properties may manifest themselves.

    ↳ quant-phgr-qchep-phActa Phys.Polon.B(2018)·12 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.